1. Field of the Invention
The present invention relates to image-forming methods and apparatuses in which surfaces of images recorded on recording media by using thermal transfer sheets are protected with protective layers formed thereon. In particular, the present invention relates to an image-forming method and an image-forming apparatus in which the surface condition of the protective layer formed over the image on the recording medium is modified to give a glossy, matte, or embossed texture, and to a surface-property-modifying sheet and a thermal transfer sheet used in the method and apparatus.
2. Description of the Related Art
Dye-sublimation-type image forming apparatuses that form images by transferring dye layers of thermal transfer sheets onto recording media have been available. In using this type of apparatus, a transparent protective layer is formed on an image formed on the recording medium to protect the surface of the image. In particular, the protective layer functions as a barrier for isolating the image from gas that causes deterioration, absorbs UV rays to prevent discoloration and fading of the image, prevents the dye or the like forming the image from migrating to other products, such as erasers, containing various plasticizers, and protects the image from sebum.
The protective layer is, for example, laminated on a ribbon-shaped substrate sheet and thermally transferred onto the image by using a thermal head. Thermal transfer of the protective layer onto the image not only helps protect the image and but also prevents the recording medium from curling or from undergoing other similar phenomena. During the thermal transfer using the thermal head, the thermal energy from the thermal head may be adequately changed to form a pattern of microscopic asperities so that the surface of the protective layer is glossy, matte, or embossed as desired.
In an existing image-forming apparatus such as one disclosed in Japanese Unexamined Patent Application Publication No. 2007-76332, a recording medium constituted by a thermoplastic substrate and a receiving layer that receives a dye is fed; a thermal transfer sheet is made to travel, the thermal transfer sheet having a dye layer and a protective layer aligned side-by-side in the travelling direction; thermal energy is applied from the thermal head while arranging the receiving layer of the recording medium to oppose the dye layer of the thermal transfer sheet so that an image is formed by heat transfer of the dye layer of the thermal transfer sheet onto the receiving layer of the recording medium; thermal energy is again applied from the thermal head while arranging the image formed on the recording medium to oppose the protective layer of the thermal transfer sheet so as to thermally transfer the protective layer of the thermal transfer sheet onto the image formed on the recording medium.